Zero insertion force connector and contact therein

ABSTRACT

A ZIF PGA socket assembly (1) includes a base housing (10) having a top surface (12) and a plurality of elongated cavities (14), and a corresponding number of contacts (100) each having a pair of elongated spaced arms (108, 110) disposed in respective cavities (14). A sliding plate (70) which designedly slidably moves on the top surface (12) of the base housing (10), has a plurality of orifices (74) therethrough in registration with the corresponding cavities (14) in the base housing (10) to not only admit conductive pins from a PGA component into the cavities (14) but also bias one arm (108) of each contact (100) to form an enlarged space between such pair of arms (108, 110) for zero insertion force for conductive pins of the PGA component when the sliding plate (70) is in an operation position. A cover (50) is mounted on the top of the sliding plate (70) for cooperation with the base housing (10) to sandwich the sliding plate (70) therebetween.

This is a division of application Ser. No. 08/093,321 filed Jul. 16,1993 U.S. Pat. No. 5,456,613.

BACKGROUND OF THE INVENTION

1. Field of The Invention

The present invention relates to zero insertion force (ZIF) connectors,especially to a ZIF pin grid array (PGA) connector including a topcover, an intermediate sliding plate and a base housing.

2. The Prior Art

PGA connectors have been developed for a long time and many U.S. Patentsare related thereto. One type generally called low insertion force (LIF)connector, is described in U.S. Pat. Nos. 3,676,832, 4,498,725,4,988,310, 5,002,499, 5,013,256, 5,057,031 and 5,092,789 wherein thecontacts are embedded within the respective cavities in the basehousing, and a sliding plate carries an above PGA electrical componenthaving a plurality of conductive pin extending downward out of thesliding plate to laterally or horizontally move with regard to the basehousing. The conductive pin of PGA can be downward inserted through theslide plate into the base housing without interference initially, andthen laterally, i.e. horizontally, moved to engage and be sandwichedwithin two horizontal resilient arms of the contact in the cavity of thebase housing subsequently. Such engagement between the conductive pin ofthe PGA component and the contact of the socket housing is in a form oflow insertion force (LIF).

The second type can been seen in U.S. Pat. Nos. 5,017,152, 5,037,321,5,059,135, 5,186,642, and 5,192,221, in which one generally verticalbeam of a pair of contact beams can be moved or deflected along with thesliding or moveable plate when such sliding plate is actuated tohorizontally move along the top surface of the base housing. Theoutwardly lateral movement of one beam of such pair of contact beamsresults in expansion of the space between such pair of beams so that theconductive pin of the PGA component can be inserted into the spacebetween such pair of contact beams in the cavity of the base housingwithout interference, i.e., zero insertion force (ZIF). Consequently,the sliding plate moves back transversely to its original position, andthe deflected beam can restore itself to the original position by itsinherent resilience and cooperate with another opposite beam toelectrically engage the inserted conductive pin of the PGA componenttherebetween.

Similar to the second type, the third type PGA connector also uses thesliding plate to movably deflect the top portion of the contact beam.Differently, the third type design generally uses a pair of slidingplates which move horizontally with regard to the base housing and inopposite directions with each other to urge such two beams of thecontact in the base housing, respectively. Hence, such pair of beams aresimultaneously outwardly biased to expand the opening therebetween toreceive the inserted conductive pin of PGA under a ZIF condition. Afterthe PGA pin is completely vertically loaded within two contact beams,both sliding plates move back in opposite directions relative to eachother, to their original positions, respectively. Therefore, such pairof contact beams restoratively move close to each other for electricallytightly engaging the conductive pin of PGA inserted therebetween. Forexample, there are U.S. Pat. Nos. 4,468,072, 4,674,811, 4,836,798,4,889,499 and 5,123,855 disclosing the similar manner.

Regardless of two-piece (i.e. one sliding plate associated with the basehousing) PGA connector or three-piece (i.e. two sliding platesassociated with the base housing) PGA connector, the respective designshave their individual advantages and disadvantages from the viewpointsof mechanical function, manufacturing process and economicconsideration.

An object of the present invention is to provide a three-piece (i.e. asliding plate sandwiched between a cover and the base housing) PGAconnector which may not only be easily and economic manufactured andassembled, but also have good function and performance in cooperationwith the PGA component.

SUMMARY OF THE INVENTION

According to the invention, a ZIF PGA socket includes a base housinghaving a top surface and a plurality of elongated cavities, and acorresponding number of contacts having a pair of elongated armsdisposed in respective elongated cavities. A sliding plate whichdesignedly slidably moves on the top surface of the base housing, has aplurality of orifices therethrough in registration with thecorresponding cavities to not only admit conductive pins from PGA intothe cavities but also bias one arm of each contact to form an expandedspace between such pair of arms of each contact for zero insertion forcefor conductive pins of the PGA component when the sliding plate is in anoperation position. A cover is mounted on the top of the sliding platefor cooperation with the base housing to sandwich the sliding platetherebetween wherein the cover and the sliding plate are commonly movedhorizontally in a same direction along the top surface of the basehousing and such horizontal movement is actuated by rotating anoperation handle of an actuation lever beside the base housing, fromwhich a transmission or cam shaft extends to push the sliding plate andthe above cover to move outwardly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded prospective view of the presently preferredembodiment of a ZIF PGA socket assembly without the contacts thereinaccording to this invention.

FIG. 2 is a prospective view of the base housing of the socket assemblyof FIG. 1.

FIG. 3 is a prospective view of the cover of the socket assembly of FIG.1 with a portion thereof cut-away to show the detent structure on theunderside.

FIG. 4 is a prospective view of the sliding plate of the socket assemblyof FIG. 1.

FIG. 5 is a prospective view of the actuation lever of the socketassembly of FIG. 1.

FIG. 6(A) is a prospective view of the contact for use within the socketassembly of FIG. 1.

FIG. 6(B) is another prospective view of the contact of the FIG. 6 (A).

FIG. 7 is a fragmentary cut-away view of the base housing of FIG. 2 toshow the retention bar and the blocks in the cavity.

FIG. 8(A) is a fragmentary cross-sectional view of the assembled socketassembly of FIG. 1 without the contacts therein when the operationhandle is in a horizontal position.

FIG. 8(B) is a fragmentary cross-sectional view of the assembled socketassembly of FIG. 1 without the contacts therein to show the cammingsection of the cam shaft of the actuation lever engaging and pushing thesliding plate forward when the operation handle is in a verticalposition.

FIG. 9(A) is a fragmentary cross-sectional view of the assembled socketassembly of FIG. 1 to show the relationships among the cover, thesliding plate, the base housing and the contacts therein when theoperation handle of the actuation lever is positioned in a horizontalposition.

FIG. 9(B) is a fragmentary cross-sectional view of the assembled socketassembly of FIG. 1..to show the relationships among the cover, thesliding plate, the base housing and the contacts therein when theoperation handle of the actuation lever is positioned in a verticalposition.

DESCRIPTION OF THE INVENTION

As shown in FIGS. 1 and 2, a ZIF PGA socket 1 of the present inventionincludes a base housing 10 including a generally square main body 12 anda plurality of cavities 14 vertically extending therethrough forreceiving the corresponding contact 100 therein, respectively. A firstset of ledges 16 are formed along the upper portion of each of the leftand right side surfaces 18. Oppositely, a second set of ledges 20 areformed along the lower portion of each side surface 18. A pair ofstandoffs 22 extend downward from the bottom surface of the middle ledge20 for abutting against the board (not shown) on which the socket 1 ismounted. A front ledge 24 extends forwardly from the lower portion ofthe front side surface 26 and plural standoffs 28 extend downward fromthe bottom surface thereof.

An elongated shroud section 30 is positioned at the rear end of thehousing 10, and has generally a U-shaped vertical cross-section taken ina lateral direction. A pair of end walls 32 and an intermediate wall 34extend upwardly from the front side portion 31 of the shroud section 30which is positioned adjacent the rear portion of the square body 12. Aprotrusion 36 upward extends from the top of a side portion of each endwall 32. By a generally U-shaped cross-section channel 38, a verticallyextending rear side portion 40 is spaced from the front side portion 31of the shroud section 30 in a front-to-back direction. A shallowhorizontal groove 42 lengthwise extends along the inner surface, whichis facing the U-shaped channel 38, of the rear side portion 40 of theshroud section 30, such that a step 44 is formed thereof. An elongatedaperture 46 is positioned beside the groove 42 and is open to thechannel 38. The groove 42 further downward extends along the innersurface of the rear side portion 40, when it reaches the right side endthereof, to form a vertical groove 43. The vertical groove 43 terminatesgenerally at the bottom midpoint of the cross-sectional configuration ofthe U-shaped channel 38.

Also with reference to FIGS. 1 and 3, a cover 50 having a generallysquare main plate 52. A vertical front wall 53, two left and right sidewalls 54 respectively extend downward from the front, the left and theright edges of the plate 52, and no vertical wall is disposed at therear edge of the plate 52. Four elongated inwardly detents 56 are atintervals positioned along the lower edge of each right side wall andleft side wall 54 for vertically latchable engagement with thecorresponding ledges 16 of the base housing 10 to prevent the cover 50from upward moving away from the base housing 10. A plurality of holes58 vertically extend through the plate 52 for corresponding to andalignment with the cavities 14 of the base housing 10, respectively. Aprotruding plate 60 horizontally rearward project from the rear end ofthe plate 52. A retention bar 62 outwardly and rearward extends at therear edge of the protruding plate 60 for reception within the aperture46 of the base housing 10 when assembled. A pair of spaced pressing bars64 are disposed on the rear end of the plate 52 and closely below theprotruding plate 60. It can be seen that the length of the bar 64 issubstantially equal to or smaller than the space between the end wall 32and the intermediate wall 34 so that bars 64 can be respectivelyreceived in such spaces without any improper interference when the cover50 is movably attached to the base housing 10. It is also contemplatedthat the length of the protruding plate 60 is smaller than the width ofthe plate 52 and substantially equal to the distance defined between thetwo protrusions 36. Hence, the protruding plate 60 may pass the spacebetween these two protrusions 36 of the base housing 10 to move from thefront side portion 31 of the shroud section 30 of the base housing 10 tothe rear side portion 40 thereof for assembling the whole socket 1.

Also referring to FIGS. 1 and 4, a sliding or moveable plate 70 issandwiched between the base housing 10 and the cover 50. The slidingplate 70 includes a generally square body 72 and a plurality of orifices74 extending therethrough in alignment with the corresponding cavities14 of the base housing 10 and the holes 58 of the cover 50. A pair ofengagement bars 76 are integrally outwardly formed at the rear edge ofthe sliding plate 70. Understandably, the length of the bar 76 issubstantially equal to or smaller than the space between the end wall 32and the intermediate wall 34 for easy passage therebetween withoutobstruction. A front and a rear lateral expansion portions 78 aredisposed on each side edge of the sliding plate 70 for properlyinterferential engagement with the inner surfaces of the cover 50 forthe purpose of guiding the siding plate 70 to move with regard to thecover 50 in a front-to-back direction.

Also referring to FIGS. 1 and 5, an actuation lever 80 includes anoperation handle 82 seated by the right side of the base housing 10. Atransmission or cam shaft 84 integrally and perpendicularly extendingfrom the rear end of the operation handle 82, includes three supportingsections 86 at intervals and two camming sections 88 intermediatebetween every two supporting sections 86, and is designedly disposed inthe U-shaped channel 38 of the base housing 10. In this embodiment, eachsupporting section 86 is of a generally fully cylinder type for completereception and support within the U-channel 38 of the base housing 10such that such supporting section 86 functions as a supporting pointwhen the operation handle 82 is pivoted around the U-shaped channel.Differently, the camming section 88 has a reduced dimension and anon-round cross-sectional configuration in comparison with thesupporting section 86. Such non-round cross-sectional shape provides thecamming section 88 with camming function when the camming section 88 andthe integral supporting section 86 are rotated about the same axis whichis axially defined at the center of the supporting section 86.

It is noted that the pair of engagement bars 76 of the sliding plate 70are designedly confronting and engaged with corresponding two separatecamming sections 88, respectively. Therefore, the sliding plate 70 canbe actuated to move forward by the camming sections 88 when the cammingsections 88 and their integral supporting sections 86 are rotated aboutthe center axis of the supporting section 86.

A rear end of the operation handle 82 is integrally and fixedlyconnected to the outermost right-hand side supporting section 86 whereina key 90 is horizontally disposed on the outermost center portion of thesemi-circle configuration of the side view of such rear end of theoperation handle 82. Hence, the innermost end 92 of such key 90 movesalong the vertical groove 43 in the right-hand side portion of theshroud section 30 while the operation handle 82 is lifted up from itshorizontal position to the vertical position. At the same time, the camshaft 84 is dependently rotated at generally 90 degrees correspondinglyfor pushing the sliding plate 70 outwardly (forwardly).

The tail portion 94 of the operation handle 82, which is close to thefree end, is upwardly offset for allowance of sufficient spacethereunder for easy operation.

Also with reference to FIGS. 6(A) and 6(B), disposed within each cavity14 of the base housing 10 is a contact 100 including a main generallysquare segment 102 having a pair of barbs 104 on two opposite sides forinterferential securement within the cavity 14 of the base housing 10. Atail 106 extends downward from the bottom of the main segment 102 forsolderable reception within a corresponding hole of a board (not shown)on which the socket is mounted. A pair of spaced active arm 108 andimmoveable arm 110 extend from the top of the main segment 102 whereinan engagement section 112 integrally and straight extendsperpendicularly from the top of the arm 108. Differently, a retentionsection 114 of two right angle bends integrally extends from the top ofthe arm 110 in the same direction of the engagement section 112 of thearm 108. The retention section 114 includes an upper horizontal section116 extending from the top of the arm 110 and generally at the sameheight as the engagement section 112. An intermediate section 118downward extends from the outermost end of the upper horizontal section116 thus forming a first right angle bend. A lower horizontal section120 extends from the lower end of the intermediate section 118 in thesame direction as the upper horizontal section 116, thus forming thesecond right angle bend. It can be noted that the total length of theupper and the lower horizontal sections 116 and 120 of the arm 110 aredesignedly generally equal to that of the engagement section 112 of thearm 108, so that the tips of the lower horizontal sections 120 of thearm 110 and of the engagement section 112 of the arm 108 are generallyaligned in the same vertical plane.

Referring to FIG. 7, to receptively comply with the contact 100, eachcavity 14 in the base housing 10 having generally a square cross sectionlengthwise, are surrounded and formed by the inner front wall 141, rearwall 142, left-hand side wall 143 and right-hand side wall 144. In thecavity 14, a pair of blocks 140 are disposed on the inner front wall 141and the rear wall 142, respectively wherein each block 140 extends fromthe bottom opening of the cavity 14 thereunto and generally terminatesat the mid-length thereof. Those two blocks 140 are integrally connectedto the left-hand side wall 143 but spaced away from the right-hand sidewall 144 by a distance. In this embodiment, such distance issubstantially equal to the thickness of the main segment 102 of thecontact 100 so that the left-hand side portion and the right-hand sideportion of the main segment 102 of the contact 100 can be securelysandwiched between the open side edges 145 of the blocks 140 and theright-hand side wall 144, respectively, for engagement in the cavity 14of the base housing 10.

It is also appreciated that the width of the main segment 102 of thecontact 100 is substantially equal to the distance defined between thefront wall 141 and the rear wall 142 such that the left and right edges107,109 of the main segment 102 of the contact 100 abut against thefront wall 141 and the rear wall 142 in the cavity 14 with theirassociated barbs 109 embedded into the corresponding front wall 141 andthe rear wall 142 for securement. Therefore, the contact 100 can besnugly and tightly retained within the cavity 14 without moving.

To correspond to the retention section 114 of the immoveable arm 110 ofthe contact 100, a retention bar 146 vertically extends along themid-region of the left-hand side wall 143 and protrudes into the cavity14. Hence, the lower horizontal section 120 of the retention section 114is aligned with the retention bar 146 in the front-to-back direction forpreventing the arm 110 from moving forwardly when a forward force actson the contact 100. Referring back to FIG. 4, relatively, each orifice74 in the sliding plate 70 originally has a generally squareconfiguration in compliance with the shape of the cavity 14 in the basehousing 10. Like the cavity 14, in correspondence to the engagementsection 112 of the arm 108 of the contact 100, an longitudinal pushingbar 75 occupies a portion of the orifice 74 and forms a groove 77 by itsside for reception of the tip of engagement section 112 of the activearm 108 of the contact 100 therein. Accordingly, the pushing bar 75actuates the engagement section 112 of the active arm 108 of the contact100 forwardly when the sliding plate 70 moves forwardly.

During assembling, the cover 50 is installed on the top of the basehousing 10 in a front-to-back direction with the bottoms of the left andright walls 54 supportively engaged with the second set of ledges 20 ofthe base housing 10 under the condition that the sliding plate 70 isplaced to be sandwiched between the base housing 10 and the cover 50. Atthe same time, the top surfaces of the detents 56 of the cover 50 engagethe bottom surfaces of the first set of ledge 16, and therefore thecover 50 can not move up and down. The cover 50 successively rearwardmoves to the shroud section 30 of the base housing 10 with the cam shaft84 of the actuation lever 80 having been placed in the U-shaped channel38 therein under the condition that the supporting sections 86 of thecam shaft 84 of the actuation lever 80 are seated against inner surfaceof the shroud section 30 facing the U-shaped channel 38, and generallyaligned with the corresponding end walls 32 and intermediate wall 34,respectively, and the camming sections 88 thereof are generally alignedwith the corresponding spaces between such end wall 32 and intermediatewall 34. As a result, the operation handle 82 is positioned in parallelrelation to the base housing 10 and the innermost end 92 of the key 90of the actuation lever 80 is received with in the vertical groove 43 ina position which is generally at the same level as the lying operationhandle 82.

Such rearward movement of the cover 50 continues until the rear edge ofthe main plate 52 of the cover 50 confronts the upper portions of theend walls 32 and the intermediate wall 34 of the base housing 10, therear edges of the side walls 54 confront the corresponding end walls 32of the base housing 10, and the front wall 53 is located on the frontledge 24 of the base housing 10. In this situation, the protruding plate60 of the cover 50 extends into the shroud section 30 of the basehousing 10 and is positioned over the U-shaped channel 38 in the basehousing 10 in the condition that the front portion of the protrudingplate 60 is seated on the top of the intermediate wall 34 and the endwalls 32 of the base housing 10, and the rear portion of the protrudingplate 60 is receptively engaged within the horizontal groove 42 in theshroud section 30 and seated on the step 44 thereof. It can beappreciated that the protruding plate 60 is retained between twoprotrusions 36 positioned respectively on the top of the end walls 32 ofthe base housing 10, and the bar 62 at the rear end of the protrudingplate 60 is designedly received within the corresponding aperture 46 inthe rear side portion 40 of the shroud section 30. Accordingly, theprotruding plate 60 covers and shields the U-shaped channel 38 and thecam shaft 84 of the actuation lever 80 therein.

It can be contemplated that two engagement bars 76 extending rearwardfrom the rear edge of the sliding plate 70 which is sandwiched betweenthe cover 50 and the base housing 10, can respectively pass the spacesdefined between the intermediate wall 34 and the end walls 32 of thebase housing 10, and project into the U-shaped channel 38 in the shroudsection 30 for confrontation with the camming section 88 of theactuation lever 80. The pressing bars 64 positioned beneath theprotruding plate 60 and extending rearward from the rear edge of theplate 52, can also respectively pass such spaces and project into theU-shaped channel 38 in the shroud section 38 but without engaging thecamming section 88 of the cam shaft 84. Naturally, the engagement bars76 of the sliding plate 70 are generally positioned below the pressingbars 64 of the cover 50, respectively, so that the pressing bars 64 ofthe cover 50 can provide guidance to the horizontal movement of theengagement bars 76 of the sliding plate 70. It is also noted that thesliding plate 70 can not move forwardly or laterally because ofconfinement of the front wall 53 and the side walls 54 of the cover 50,and also not move rearward due to confrontation of the rear edge thereofwith the intermediate wall 34 and the end walls 32 of the base housing10. In this situation, the holes 58 in the cover 50, the correspondingorifices 74 in the sliding plate 70, and the corresponding cavities 14in the base housing 10, are generally aligned together in a verticaldirection, respectively, for respective reception of the correspondingcontacts 100 and the downward extending conductive pin of PGA components(not shown).

Finally, the contacts 100 are inserted into the cavities 14 in the basehousing 10 from the bottom. As aforementioned, the main body 12 of eachcontact 100 can be retained within the corresponding cavity 14 with theengagement of the associated opposite side barbs 109. The engagementsection 112 of the active arm 108 and the upper horizontal section 116of the retention section 114 of the immoveable arm 110 of each contact100 further upwardly project into the corresponding orifice 74 in theabove sliding plate 70 wherein the tip of the engagement section 112further horizontally projects into the groove 77 in the orifice 74. Thetails 106 of the contact 100 downward extend out of the base housing 10for solderably mounting to the PC board on which the socket 1 is seated.

Referring to FIGS. 8(A) and 8(B), when the PGA component is intended tobe electrically engaged with and mounted on the socket 1, the cam shaft84 of the actuation lever 80 is itself rotated at generally 90 degreesthrough the operation handle 82 of the actuation lever 80 being upwardpivoted from the forward or horizontal position to the upward orvertical position by serving the supporting section 86 of the actuationlever 80 as the supporting point in the U-shaped channel 38.Accordingly, the camming section 88 of the cam shaft 84 associativelyrotates at generally 90 degrees within the channel 38 and its rotationsimultaneously actuates the engagement bars 76 of the sliding plate 70to move forwardly with regard to the base housing 10 due to the cammingsurface thereof.

As shown in FIGS. 9(A) and 9(B), the forward movement of the slidingplate 70 causes the engagement section 112 of the active arm 108 of eachcontact 100 to also deflect forwardly because the retention bar 146within each orifice 74 engages and pushes forwardly the tip of thecorresponding engagement section 112 of the contact 100 which ispositioned within the groove 77 in the orifice 74. Differently, theforward movement of the sliding plate 70 does not push the retentionsections 114 of the immoveable arm 110 forwardly because the inner rearwall surface 73 of the sliding plate 70 which defines such orifice 74,is relatively far from the retention section 114. It can be seen in FIG.9(B) that the inner wall surface 73 facing the orifice 74 just slightlyconfronts the retention section 114 of the immoveable arm 110 when thesliding plate 70 is in its final outermost position so that it isunderstood that the retention section 114 of the immoveable arm 110 isnot forced by the sliding plate 70.

Moreover, even though the active arm 108 is actuated to deflect forwardby the sliding plate 70, the retention bar 146 in the cavity 14 preventsthe immoveable arm 110 of the contact 100 from moving forwardly under aforward movement intention incurred by forward deflection of the activearm 108 of the contact 100. Accordingly, for each contact 100, thedistance or the space between the upper horizontal section 116 of theretention section 114 of the immoveable arm 110 and the engagementsection 112 of the active arm 108 increases by the forward deflection ofthe active arm 108. Such enlarged space (or distance) is bigger than thedimension (or diameter) of the conductive pin of the PGA component whichis to be inserted into the socket 1, such that the insertion of theconductive pin can be achieved without interference through zeroinsertion force (ZIF). Therefore, the socket 1 with its associated innercontacts 100 can be deemed as in such a fully open position or in anoperative state for loading the PGA component, as shown in FIG. 9(B).

Referring to FIGS. 9(A) and 9(B), it is also noted that the cover 50 isalso forced to move forward by the forward moving sliding plate 70 whenthe front edge of the forward moving sliding plate 70 confronts thefront wall 53 of the cover 50. Accordingly, the cover 50 and slidingplate 70 both moves forward with regard to the base housing 10.

When the PGA component is adequately seated on the socket 1, eachconductive pin thereof is inserted through the corresponding hole 58 inthe cover 50 into the corresponding orifice 74 in the sliding plate 70and positioned in the space between the upper horizontal sections 116 ofthe immoveable arm 110 and the engagement section 112 of the active arm108 of the contact 100 inserted therein. The tip of the conductive pinof the PGA component may further project into the cavity 14 in the basehousing 10. Successively, the operation handle 82 of the actuation lever80 is downward pivoted from the upward position to the forward position,so that the associated camming section 84 is also rotated at generally90 degrees back to its original position. Therefore, the camming surfaceof the camming section 88 retreats rearward in the horizontal directionthus disengaging the engagement bars 76 of the sliding plate 70therefrom. Then, the sliding plate 70 is forced to move rearward by theinherent resilient forces exerted by the deflected active arms 108 ofthe contacts 100 because of the engagement of the pushing bar 75 withthe engagement section 112 of such deflected arm 108 in each orifice 74in the sliding plate 70. Accordingly, the sliding plate 70 is moved backto its original position.

When the deflected arm 108 and its associated engagement section 112spring back to their normal positions, the inserted conductive pin ofPGA component confronts and is successively pushed by the rearwardmoving engagement section 112 of the active arm 108 of the contact 100to move rearward. It can be understood that because each conductive pinof PGA component is snugly positioned within a properly-sized hole 58 inthe cover 50, the rearward movement of each conductive pin of PGAcomponent almost simultaneously presses the inner surface of the cover50 around the hole 58 in a front-to-rear direction, thus pushing thewhole cover 50 rearward until the cover 50 is moved back to its originalposition. When the whole socket 1 is restored, the socket 1 and itsassociated inner contacts 100 can be deemed as in such a fully closedposition or in a non-open state for signal transmission. In thissituation, the conductive pin of PGA component is, electrically andmechanically, tightly sandwiched between the engagement section 112 ofthe active arm 108 and the upper horizontal section 116 of the retentionsection 114 of the immoveable arm 110 of the contact 100 because theoriginally designed distance therebetween is somewhat smaller than thediameter of the conductive pin of the PGA component. Therefore, areliable and good electrical engagement is obtained between the socket 1and the PGA component.

It can be understood that the replacement or the unloading of the PGAcomponent on the socket 1 can be achieved by repeating the foregoingsteps on a ZIF basis.

To limit the movement of the cover 50 with regard to the base housing 10in the front-to-rear direction, there is a boss 17 (only one shown)positioned on each side surface 18 of the base housing 10 for designedlyrelatively moving within the last two adjacent rear detents 56 on thesame side of each side wall 54 of the cover 50 within a limited distancedefined between such two detents 56. This feature prohibits the cover 50from moving forward too far or even leaving from the base housing 10when there is no PGA component loaded thereon. Based on this feature,there is an interference fit occurring between the last rear detent 56on each side wall 56 of the cover 50 and the boss 17 located on the sameside surface 18 of the base housing 10 when the cover 50 is installed onthe base in the front-to-rear direction.

To retain the operation handle 82 in the horizontal position formaintaining the whole socket assembly 1 in a reliable stable manner, anembossment 55 is positioned on the outer surface of right side wall 54to incorporate a recess 83 in the operation handle 82, thus latching theactuation lever 80 with the base housing 10 without a risk of improperupward rotation. This feature also causes an interference occurringbetween the embossment 55 of the cover 50 and the recess 83 in theoperation handle 82, when such operation handle 82 is lifted up orpushed down. The operation handle 82 of the actuation lever 80 can lieon the second set middle ledge 20 of the base housing 10 for keepingitself in the horizontal position without the possibility of downwardrotation. It is appreciated that the cooperation of the key 90 of theactuation lever 80 and the vertical groove 43 in the shroud section 30can guide the rotation of the actuation lever 80 and limit the upwardmovement of the operation handle 82. Moreover, when assembly, theengagement bars 76 of the sliding plate 70 is sandwiched between twoadjacent supporting sections 86 of the cam shaft 84, so that theactuation lever 80 can not move in the direction along the channel 38.

The specific contours of the center opening 11 in the base housing 10and of the center opening 71 in the sliding plate 70 are designed tomaximize the dimensions of such openings for customary use whilemaintaining the strength of the base housing 10 and the slide plate 70.

It is also seen that the through-holes HI in the cover 50, thethrough-holes H2 in the sliding plate 70, and the staggeringarrangements of the first set of ledges 16 with the second set of ledges20, are all designedly configured for the consideration of moldingprocess.

It may be experienced that if the lengths of two arms 108,110 of thecontact 100 become relatively greater than the height of the mainsegment 102, the arm 110 may move in an opposite direction, i.e.,rearward, when the arm 108 is pushed by the sliding plate 70 forward. Inthis situation, the retention bar 146 in the cavity 14 may no longerfunction as a stopper, but still may function as an guiding bar toincorporate the retention section 114 of the arm 110 and the engagementsection 112 of the arm 108 for orientation when the contact 100 isloaded into such cavity 14 from the bottom during assembling.Alternately, in a simplified design without consideration of orientationof the contact in assembling, the lower horizontal section 120 and theimmediate section 118 of the arm 110, and the retention bar 146 in thecavity 14 in the base housing 10 may optionally be removed therefrom inthe foregoing situation.

It can be noted that the present invention is different from theaforementioned three type prior art socket assemblies. The presentinvention uses a three-piece socket assembly 1, i.e., the base housing10, the sliding plate 70 and the cover 50, wherein the sliding plate 70is adequately slidably sandwiched between the base housing 10 and thecover 50. The sliding plate 70 in the present invention only confrontsthe horizontal pushing forces without interests in how to combine thesliding plate to the base housing. Differently, in the first and thesecond type prior art socket assemblies, the sliding plate itself needsto provide relevant mechanism for directly or indirectly securelymounting on the base housing. Also, the cover 50 in the presentinvention does not exert forces on the contacts to deflect the contactsfor zero insertion force. This is different from the third type priorart socket assembly in which two sliding plates respectively actuatesthe corresponding contact arms or beams to move in opposite directionsfor expansion the space therebetween for zero insertion force. Inconclusion, in the present invention, the sliding plate only functionsas and performs horizontal movement without redundant mechanism forsecurement, and the cover only provides the securement, for helping thesliding plate stably horizontally sliding on the base housing, withoutactuating the contacts directly.

While the present invention has been described with reference to aspecific embodiment, the description is illustrative of the inventionand is not to be construed as limiting in the invention. Variousmodifications to the present invention can be made to the preferredembodiment by those skilled in the art without departing from the truespirit and scope of the invention as defined by the appended claims.

Therefore, persons of ordinary skill in this field are to understandthat all such equivalent structures are to be included within the scopeof the following claims.

What is claimed is:
 1. A contact for use with a PGA socket assembly,comprising:a flat main square segment having barbs positioned on twoopposite sides; a tail extending downwardly from a bottom portion of thesquare segment for reception in a hole in a PC board on which the socketassembly is mounted; and an active arm and an immovable arm respectivelyextending upwardly from a top portion of the square segment and spacedfrom each other for clamping a conductive pin extending downwardly froma PGA component; wherein said active arm has an engagement sectionextending from a top portion thereof in a first direction perpendicularto the main square segment, and said immovable arm has a retentionsection including two ends, wherein one of the ends integrally formedwith a top end of the immovable arm; and wherein the retention sectionof the immovable arm comprises an upper horizontal section which ispositioned at a same height as the engagement section of the active arm,an intermediate section extending downwardly from one distal end of theupper horizontal section of said retention section of the immovable arm,and a lower horizontal section horizontally extending from a lower endof the said intermediate section in the same first direction.
 2. Thecontact as described in claim 1, wherein an outer end of the lowerhorizontal section and an outer end of the engagement section aresubstantially positioned at a same vertical plane.
 3. A contact (100)for use within a PGA socket assembly for receiving a pin type PGAcomponent, comprising:a flat main square segment (102) having barbs(104) positioned on two opposite right and left edges (107, 109),respectively; a tail (106) extending downwardly from a bottom portion ofthe main square segment (102); a first arm (108) and a second arm (110)parallel to and spaced from each other, and both extending upwardly froma top portion of the main square segment (102) wherein the main squaresegment (102), the tail (106) and said first arm (108) and said secondarm (110) are generally in vertically a coplanar manner; and a firsthorizontal section (112) horizontally extending, by bending, from a topend of the first arm (108) in the first direction, and a secondhorizontal section (116) horizontally extending, by bending, from a topend of the second arm (110) in the same first direction, whereby thefirst horizontal section (112) and the second horizontal section (116)being generally at a same height and having a farthest distance withregard to the main square segment (102), commonly define therebetween aspace which is somewhat smaller than a diameter of a conductive pin ofthe PGA component so that said conductive pin can be electrically andmechanically tightly sandwiched between the first horizontal section(112) and the second horizontal section (116).